In recent years, for example, as a communication means of inter-vehicle communication, communication in an isolated district with no network infrastructure, and a communication means at the time of disaster, mobile ad-hoc networks (MANET) have been spotlighted. In the MANET, a number of communication terminals (nodes) are desired to be wirelessly connected to one another.
In the MANET, movement and wireless connections of communication terminals are assumed. Therefore, due to the movement of the communication terminals and wireless interference, there may occur a failure such as loss of packets (communication data), an increase in communication delay, and communication interruption. In such a case, existing communication protocols do not operate well.
For example, Transmission Control Protocol (TCP) is a communication protocol commonly used in wired environments. TCP is called a connection-oriented protocol. TCP has characteristics, for example, in performing establishment of communication sessions, control of communication speeds, and retransmission control of packets. When TCP is used in a MANET environment, it is well known that communication is not smooth due to packet loss and communication interruption which occur at a high probability.
An example of a technique for avoiding such a state in which communication is not smooth is disclosed in PTL 1. A wireless communication device disclosed in PTL 1 monitors a window size of TCP. When determining that a congestion state has occurred, the wireless communication device uses UDP (User Datagram Protocol) which is another communication protocol. PTL 1 also discloses a method for continuing communication by performing TCP communication and UDP communication in parallel.
PTL 2 discloses a communication device that controls wireless connection parameters so that interference among a plurality of simultaneous wireless connections is reduced.
PTL 3 discloses a communication system that selects transmission parameters on the basis of estimated throughput. The communication system obtains the estimated throughput on the basis of an estimation error rate and a data transmission rate.